The present invention generally relates to the field of machining of materials and, more particularly to the diamond turning of materials which detrimentally react with diamond.
Diamond turning is an enabling technology for the production of aspherical optical surfaces, and for other extremely precise machining of surfaces and contours. However, the process has been historically restricted to a small group of materials that are "diamond turnable," that is, materials which do not cause extremely rapid wear of the diamond tool.
This small group of materials typically includes coppers, aluminums, and some nickels, as well as certain plastics, crystals and salts. Many other materials possess more desirable engineering properties, but cause this high rate of wear of diamond tools which precludes useful results. Important examples of materials which cannot currently be efficiently diamond turned are the ferrous materials (i.e. steels and irons). Steels, especially stainless steels, would find a multitude of new applications if it could be diamond turned. For one example stainless steel could be used as molds for aspheric lenses, if it were possible to produce the desired shape to optical class tolerances.
It has been shown that one reason why many materials (especially metals) are not diamond turnable is that the material reacts chemically and detrimentally with the element carbon, which the diamond tool comprises. This detrimental chemical wear may be accompanied by dissolution and diffusion. These reactions cause extremely rapid wear of the tool. It is also known that, in general, the rates of chemical processes are temperature dependent, and that lowering of temperature sharply retards the rate of chemical reaction.
The present invention allows diamond turning of materials which were previously considered non-diamond turnable by providing a method and apparatus for chilling the diamond tool and the workpiece to cryogenic temperatures. This retards the wear rate of the workpiece which is due to reaction with the carbon in the tool to a rate which is comparable with the normal wear due to microfracture, fatigue, or other wear causing mechanisms.
It is an object of the present invention to provide apparatus which will allow the efficient machining of materials which are presently considered to be non-diamond turnable.
It is another object of the present invention to materials which are presently considered to be non-diamond turnable by providing a method and apparatus for chilling the diamond tool and the workpiece to cryogenic temperatures. This retards the wear rate of the workpiece which is due to reaction with the carbon in the tool to a rate which is comparable with the normal wear due to microfracture, fatigue, or other wear causing mechanisms.
It is an object of the present invention to provide apparatus which will allow the efficient machining of materials which are presently considered to be non-diamond turnable.
It is another object of the present invention to provide apparatus for the machining of optical quality complex forms out of materials which are presently considered to be non-diamond turnable.
Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.